Doctors generally agree that such factors as cigarette
smoking, eating rich foods high in fats, and alcohol
consumption not only do damage by themselves
but also aggravate genetic predispositions toward
certain diseases.

(A) not only do damage by themselves but also
aggravate
(B) do damage by themselves but also are
aggravating to
(C) are damaging by themselves but also are
aggravating
(D) not only do damage by themselves, they are
also aggravating to
(E) are doing damage by themselves, and they are
also aggravating

My doubt is in the non- underlined portion : Are cigarette
smoking, eating rich foods high in fats, and alcohol
consumption are in parallel??

Plz let me know what sort of parallelism is maintained?? I am confused!